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Québec, Canada

Galvez-Cloutier R.,Laval University | Saminathan S.K.M.,Laval University | Boillot C.,Laval University | Triffaut-Bouchet G.,CEAEQ | And 2 more authors.
Environmental Management

Increasing phosphorus (P) content and decreasing water quality of Saint-Augustin Lake, Quebec City, Canada, has led to implementation of an Integrated Watershed Management Plan to restore the lake. As a part of the plan, the effects of different restoration techniques on lake water quality and biological community (i.e., biological compatibility) were assessed during an isolated water enclosure study and laboratory microcosm assay, respectively. The restoration techniques include: (i) coagulation of P by alum only (20 mg L -1), (ii) active capping of sediments using a calcite layer of 10 cm, and (iii) a complete method involving both alum coagulation and calcite capping. The results showed that the total P (TP) was greatly decreased (76-95 %) by alum + calcite, followed by calcite only (59-84 %). Secchi depth was 106 % greater and chlorophyll a concentrations were declined by 19-78 % in the enclosure which received both alum and calcite. Results of the biological compatibility test showed that total phytoplankton biomass declined by 31 % in microcosms composed of alum + calcite. No significant (P>0.05) toxic effect was found on the survival of Daphnia magna and Hyalella azteca in both alum only and alum + calcite microcosms. Although the alum + calcite technique impaired the survival of Chironomus riparius, the midge emergence was much higher compared to alum only and control. Overall, the alum + calcite application was effective in controlling P release from sediment and lowering water column P concentrations, and thus improving the water quality and aquatic life of Saint- Augustin Lake. However, the TP concentrations are still higher than the critical limit (20 lg L-1) for aquatic life and the water column remained in the eutrophic state even after treatment. Increased TP concentrations, to higher than ambient levels of the lake, in the water column of all four enclosures, due to bioturbation artefact triggered by the platform installation, likely cause insufficient dosages of alum and/or calcite applied and reduced their effectiveness. © 2012 Springer Science+Business Media, LLC. Source

Masson S.,Aquarium du Quebec | Desrosiers M.,University of Montreal | Pinel-Alloul B.,University of Montreal | Martel L.,CEAEQ

There is still no assessment of the impact of sediment chemicals and environmental conditions on macroinvertebrates at the scale of the St. Lawrence River. In order to assess these impacts in the fluvial section of the St. Lawrence River including the Montreal harbour, the community structure of macroinvertebrates using different taxonomic aggregations (genus and family) and taxa attributes (abundance, presence-absence, indicator taxa) was assessed. The goal of the study was to determine the indicator taxa of macroinvertebrates along the fluvial continuum and relate changes in macroinvertebrate community to sediment chemical conditions and environmental characteristics of habitats using variance partitioning. This study also evaluated which taxonomic level and taxa attributes of macroinvertebrates were the most suitable for bioassessment of quality of sediments and habitat environment in the St. Lawrence River. Four different macroinvertebrate assemblages were found distributed along the fluvial continuum using either abundance or presence-absence data and genus or family levels. Indicator taxa characteristic of the different macroinvertebrate communities were associated with the sediment contamination gradient. However, habitat environmental characteristics (water masses, sulphur and DOC in sediments) had more influence on macroinvertebrate assemblages than sediment contamination. Our study confirms that family level analysis can give information comparable to the genus level analysis using presence-absence or abundance of macroinvertebrates, yet a higher number of indicator taxa were detected at the genus level. © Springer Science+Business Media B.V. 2009. Source

Gruyer N.,CEAEQ | Dorais M.,Agriculture and Agri Food Canada | Bastien C.,CEAEQ | Dassylva N.,CEAEQ | Triffault-Bouchet G.,CEAEQ
Acta Horticulturae

Recently silver nanoparticles (AgNPs) were used in the preparation of new pesticide and insecticide formulations. As most of the greenhouse crops are grown hydroponically, these AgNPs may be easily found in the rhizosphere and plant organs. Because of its property, AgNPs improves the bactericidal and fungicidal effectiveness of silver against important plant pathogenic fungi. However, there has been a few reported studies of the impact of AgNPs on vascular plants, showing that AgNP could have positive or negative effects on plant growth. The aim of this study was to assess the AgNP impacts on greenhouse grown species (radish and lettuce) using barley as a reference plant. Short term effect of four silver nanoparticle concentrations (1; 2.5; 5 and 10 mg L-1) of 10 nm-PVP on the germination and root elongation were investigated under controlled growing conditions. Results on the impact of AgNPs on root elongation showed both, positive and negative effects depending of the studied species. Specifically, root length was increased for barley, but was dramatically inhibited for lettuce. However, root and leaf length of our germination trials were not affected when AgNPs were incorporated into the soil. Source

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